The present invention relates to a mechanical shock absorber or arrestor positioned between a fixed point and a movable constructional element, e.g. a pipe line and the like, to absorb a sudden shock which may arise, for example, from a pressure wave of an explosion or by earth quakes or the like. In normal service, the relative movement between the fixed point and the movable element is acceptable.
Mechanical shock absorber of different types have been known for the above-mentioned purpose. The casing of the shock absorber may be of a telescopic design, and the axial movement of an element connected to the casing, e.g. of a spindle, is converted into a rotary movement of another element connected to another part of the casing, e.g. a spindle nut, by interdisposition of a blocking action. Upon surpassing a predetermined acceleration of the movable structural element, the mechanical shock arrestor is blocked up to form a rigid support between the fixed point and the movable element. Between the two clamping points of the shock absorber a force is built up by the blocking action. Only by the substantially complete diminishing of said force is the blocked condition of the shock absorber cancelled.
In known mechanical shock absorbers of this type, an additional device for arresting shocks from the outside is provided. Moreover, a spindle with left-hand or right-hand threads can be used. In another mechanical shock absorber, two spindles are provided which can be brought into operative connection by means of additional devices. All of the known mechanical shock absorbers have the common problem that they are relatively complicated.
Accordingly, it is an object of the present invention to provide a mechanical shock absorber or arrestor of the type mentioned hereinabove, which has a construction which is simple and requires a relatively small number of elements relative to prior art shock absorbers.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The mechanical shock absorber of the present invention is characterized in that the spindle portion thereof has a thread coacting with a spindle nut by contact engagement and by rolling friction, and further has at least another thread in which another spindle nut engages by providing an axial air gap therebetween of a predetermined size, the first spindle nut being spring biased and not operatively effective as to its conversion of motion in the case of an axial shock.
The configuration of the mechanical shock absorber of the present invention permits an essentially simpler construction. In the proposed single-spindle system of the present invention, the resulting embodiment is compact as to the length and width of the housing and the shock arrestor operates reliably and substantially maintenance-free. The device also possesses a high sensitivity of response, operates in the same manner in the direction of pressure and traction and functions substantially independently from the mounting position.
The single-spindle system of the mechanical shock absorber of the present invention can also be advantageously devised to provide a double-threaded spindle in which the one thread coacts with a first spindle nut and another thread coacts with a second spindle nut. It is also possible to provide a single-thread spindle comprising a flank portion which coacts with the first spindle nut. Another threaded flank portion provided in the same thread coacts with the other spindle nut.
According to another feature of the present invention, the first spindle nut contains pins distributed on its periphery and adapted to engage with the appertaining spindle thread, said pins being spring biased in the axial direction and supported in radial and axial bearings. The first and second spindle nut may form one unit. As a result, the construction is more economical and further simplified.
The construction of the present invention allows to optionally distribute the conditions of mobility for the spindle and the spindle nut. It is preferable to provide a pivotable spindle wherein the spindle nut should be axially displaceable. It is also possible to provide an axially displaceable spindle while the spindle nuts are pivotable.
In another embodiment of the present invention, in connection with the two-threaded spindle, one of the threads can be trapezoidal in shape for cooperating with the other spindle nut, whereas the second thread can be devised as a ball threaded spindle. In this case, the spindle nuts are pivotable as separate elements, and connected by axial anchors while being under a spring bias in axial direction.
It is desirable to ensure that the spindles or spindle nuts are placed under attenuation for the acceptance of the load by means of springs disposed for opposite axial motion.